The exit command is used to stop the php program. It is not a frequently used command, but depending on the result of a function, the program may be stopped and used in such cases.
 

example:

<?php 
    echo "Start \n";
    echo "Hello World! \n";
    exit;
    echo 'Finish';
?>

output:

Start 
Hello World! 

No command will run after the exit command.